Epidermal-thyroid relationships were studied in thyroidectomized (Tx) Ptyas korros kept at 23 degrees C by observing changes in shedding frequency (SF), body weight, oxygen consumption rate (OCR), and postsurgical survival. Tx animals showed increased SFs but lost weight and eventually died, as did Tx animals receiving 3-mono-iodotyrosine injections. However, injections of 3, 5-diiodothyronine inhibited shedding and the animals survived longer. OCRs were similar in all control and experimental groups. It is concluded that among thyroid secretions, only iodothyronines inhibit shedding. Snake shedding is concluded not to reflect general metabolic status as it does in lizards.